The present invention relates to a highly packed fiber bundle contactor, and a static liquid-liquid contacting method using the fiber bundle contactor. The invention also relates to a manufacturing method for producing the highly packed fiber bundle contactor.
In order to separate or purify components of homogeneous mixtures, a liquid-liquid extraction, i.e. a solvent extraction, is frequently used. The extraction procedure involves the redistribution of the desired components between two liquid phases which are in contact with each other but are immiscible due to differences the mutual chemical or physical properties of the phases. Liquid-liquid extraction is applied in numerous chemical industries, including pharmaceutical and biomedical industries to produce pure chemical compounds, heavy organic and analytical chemistry, waste purification, etc.
In the liquid-liquid extraction process presently known in the art, one phase must be dispersed in the other phase in droplets by physical agitation to generate a large material transfer area for mass transfer of the desired components between the two phases. In general, the smaller the droplet size, the greater the transfer. There are many kinds of mechanically agitated contactors known in the art for generating small droplets, for example a simple impeller in a unit tank, a mixer-settler, a rotating disc contactor, an Oldshue-Rushton contactor, a Kuhni extractor, an AKUFVE system using centrifugal force, a sieve-plate pulsed column, etc. Each has its own advantage and disadvantage, depending on the exact structure and purpose for which it is used. Most, however, are complicated in structure and large in size so that they are not suitable for treatment of small volumes of material. In addition, if the device is installed at a location difficult to access (such as a radioactive area), it may be difficult to fix any mechanical troubles.
There are non-mechanically agitated contactors which overcome some of the disadvantages associated with mechanically agitated contactors. Examples of non-mechanically agitated contactors include spray columns and packed columns. Their main advantage is the absence of mechanical moving parts. In the spray column, one phase is dispersed as drops that move up through the continuous phase as a result of the difference in phase densities between the two phases. However, such contactors do not have a large liquid-liquid contacting area per unit volume, compared with mechanically agitated contactors, because the lack of mechanical agitation results in a greater droplet size which reduces the surface area of the dispersed phase, resulting in reduced contact between the dispersed phase and the desired components.
A conventional packed column is simply a spray column whose shell is filled with packing pieces. The packing of the spray column reduces axial mixing within the column, lengthens residence time of flowing phases, and causes distortion of the dispersed drops. This results in an increase of mass transfer rate. However, the packing itself also reduces the area available for the flow of liquid phases such that throughput is decreased and flooding can more easily occur.
Another non-mechanically agitated contactor is the Kenics mixer, also called a motionless mixer. In this mixer, the liquids are pumped concurrently through a tube containing a series of helical shaped elements which cut the flow of the liquid phases and bring the liquids into more intimate contact. The maintenance and operation of the equipment is relatively simple, and flooding is avoided.
Contactors are known in the art which are based on the use of fiber bundles (see U.S. Pat. Nos. 3,754,377; 3,758,404; and 3,839,487). In these contactors, a series of thick fiber strands are inserted into a column. The strands are not compressed, but instead maintain their individual integrity. When the ends of the fibers are soaked in a first liquid, the liquid wets the fiber strands and moves to the other end of the tube by capillary action induced by small pores within the fiber strands, comparable to the action of a wick in a kerosene lamp. A second liquid is contacted with the tube, but made to flow around the fiber strands so as to be contacted with the first liquid contained within the fibers at the surface of the fiber strands. The flow rate of the second liquid flowing around the fiber strands is controlled by a pump, while the flow rate of the first liquid within the fiber strands is controlled by the capillary action within the fibers. Therefore, in order to process a great quantity of liquid, a very wide column is required for increasing the flow quantity of the first liquid flowing within the fiber strands. This results in the need of a large apparatus.
In all of the liquid-liquid contactors mentioned above which rely on agitation of the liquid phases, i.e. mechanically agitated contactors, the agitation of the two liquid phases generates the dropwise dispersion of one phase into the other phase. This process is accompanied by the endless breakage and coalescence of the drops. The amount of dispersion of the dispersed phase depends on the density difference between the two phases, interfacial tension, viscosity, and so on. Information on dispersion, such as the drop size and distribution during agitation, which are important variables in the liquid-liquid extraction systems mentioned above, is required for analyses of the hydrodynamics and the mass transfer. However, obtaining such data is often not easy, and requires effort. In addition, since almost all of the contactors mentioned above (with the notable exception of the Kenics mixer) utilize the density differences of the two liquid phases under the effects of gravity, these apparatuses must have a vertical shape, which thereby restricts the use of work space for a particular series of experiments.
It is an object of the present invention to minimize or eliminate the problems associated with liquid-liquid contactors known in the art.